1. Field of the Invention
This invention relates to a technical field of rotation control. More particularly, it relates to a technical field of suppressing vibrations generated on rotating a rotating member exhibiting unbalanced weight.
2. Description of the Related Art
Many industrial machines, electrical devices for household use or computers are provided with a rotating member run in rotation by e.g., a motor. For example, an optical disc player device, provided on a computer, runs an optical disc, as a signal recording medium, in rotation by a disc rotation control device.
The optical disc player device has an optical pickup for illuminating a laser light beam on an optical disc run in rotation by the disc rotation control device. The disc rotation control device has a disc table for loading the optical disc thereon and a spindle motor for running the disc table in rotation.
The optical pickup includes a light source for illuminating a laser light beam on the optical disc and a photodetector for receiving the laser beam reflected on the signal recording surface of the optical disc. The optical pickup and the disc rotation control device are loaded on, for example, a mechanical chassis. This mechanical chassis supports the optical pickup for movement into and out of contact with the fixedly supported disc rotation control device.
With the above optical disc player device, the laser light outgoing from the optical pickup is illuminated on the optical disc run in rotation by the spindle motor for recording/reproducing data.
Between the mechanical chassis, carrying the optical pickup and the disc rotation control device, and a main body portion of the chassis, secured to the main body portion of the device, there is mounted a damper, supported in a floating fashion. By this floating support, the mechanical chassis cannot transmit vibrations from outside to the optical pickup.
There are occasions wherein an optical disc undergoes weight unbalances during manufacture. If an optical disc exhibiting this unbalanced weight is run in rotation, this optical disc 101 is oscillated along with a turntable 103 mounted on an end of a spindle shaft 102, as shown in FIG. 1, because the center of rotation and the center of gravity of the disc are not in coincidence with each other. In this case, the optical pickup cannot realize focusing of the optical disc with respect to the signal recording surface of the optical disc.
Moreover, the amount of the weight unbalance of an optical disc tends to be varied from one optical disc to another. Recently, it has become possible to record/reproduce data for an optical disc at an elevated speed. However, if the number of revolutions is increased, an optical disc undergoes severer vibrations.
That is, failing suitable vibration suppressing means for the existing amount of unbalanced weight or the number of revolutions of the optical disc, the optical disc undergoes vibrations, as discussed above.
Meanwhile, it is difficult to suppress vibrations due to offset of the center of gravity by increasing control capability of the damper or rigidity of operating members. On the other hand, since the rotating members are used in many fields, typified by industrial machines or electrical devices for household use, it is desirable for the rotation control device to be flexibly applied to many types of devices.